1. Field of the Invention
The present invention relates to a UWB MIMO antenna, and in particular relates to a UWB MIMO antenna with improved signal isolation.
2. Description of the Related Art
Ultra-wideband antenna is an antenna with operation band covering 3.1˜10.6 GHz. Conventionally, the Ultra-wideband multi-input multi-output antenna (UWB MIMO) antenna utilizes same-shaped radiators arranged along polarization directions perpendicular to each other to provide Ultra-wideband multi-input multi-output transmission.
FIG. 1a shows a conventional UWB MIMO antenna 1. The UWB MIMO antenna 1 comprises a first ground element 10, a second ground element 20, a first radiator 30 and a second radiator 40. The first radiator 30 is partially corresponded to the first ground element 10. The second radiator 40 is partially corresponded to the second ground element 20. The first radiator 30 is disposed along a first direction (Y), and the second radiator 40 is disposed along a second direction (X). The first direction (Y) is perpendicular to the second direction (X). The UWB MIMO antenna 1 transmits signals with perpendicular polarization directions via the first radiator 30 and the second radiator 40.
To isolate the first radiator 30 from the second radiator 40, the distance between the first radiator 30 and the second radiator 40 is increased, which increases the dimensions of the UWB MIMO antenna 1. For such a structure, signal isolation of the conventional UWB MIMO antenna 1 is weak. Specifically, mutual coupling in an operation band is about −15 dB. With reference to FIG. 1b, correlation coefficient (computed from S-Parameter) of the UWB MIMO antenna 1 in an operation band is up to 0.06.